A mutation in vesicular acetylcholine transporter increases tubulin acetylation compromising axonal transport

Abstract

ABSTRACTKinesin-3 UNC-104(KIF1A) is the major transporter of synaptic vesicles and genetic defects in this motor are linked to Charcot-Marie-Tooth disease and hereditary spastic paraplegia. In a candidate screen for genes causing neurotransmission defects inC. elegansand simultaneously affecting post-translational modification of tubulin, we identified alleleunc-17(e245) significantly elevating tubulin acetylation in neurons. UNC-17 encodes for a VAChT (vesicle acetylcholine transporter) and its human ortholog is implicated in Alzheimer’s disease. Elevated tubulin acetylation compromises motility of UNC-104 as well its cargo RAB-3. Motility of UNC-104 improves when knocking down alpha-tubulin acetyltransferase MEC-17(ATAT1) inunc-17(e245) strains. Conversely, motility of UNC-104 is negatively affected when overexpressing MEC-17 in wild type animals. Critically, transport defects are comparable when exposing nematodes to drugs that inhibit ACh neurotrans-mission. Both UNC-104 and UNC-17 as well as UNC-104 and MEC-17 colocalize in neurons and bimolecular fluorescence complementation assays (BiFC) reveal physicalin situinteractions between UNC-104/UNC-17, UNC-104/MEC-17 and UNC-17/MEC-17. We propose a model in which reduced expression of UNC-17 frees MEC-17 from the UNC-104/UNC-17 complex. This leads to increased tubulin acetylation, which in turn negatively affects UNC-104 motility.Graphical abstract